Environmental enrichment facilitates electric barrier induced heroin abstinence after incubation of craving in male and female rats

Background: Treatment strategies that aim to promote abstinence to heroin use and reduce vulnerability to drug-use resumption are limited in sustainability and long-term efficacy. We have previously shown that environ-mental enrichment (EE), when implemented after drug self-administration, reduces drug-seeking and promotes abstinence to cocaine and heroin in male rats. Here, we tested the effects of EE on abstinence in an animal conflict model in males and females, and after periods where incubation of craving may occur. Methods: Male and female rats were trained to self-administer heroin followed by 3 or 21 days of a no-event-interval (NEI). Following NEI, rats were permanently moved to environmental enrichment (EE) or new stan-dard (nEE) housing 3 days prior to resuming self-administration in the presence of an electric barrier adjacent to the drug access lever. Electric barrier current was increased daily until rats ceased self-administration. Results: We found that 21 days of NEI led to significantly greater heroin self-administration and a trend toward shorter latencies to emit the first active lever press in the first abstinence session compared to 3 days of NEI. EE, when compared to nEE, led to longer latencies in the first abstinence session. Also, EE groups of both sexes and in both NEIs achieved abstinence criteria in significantly fewer numbers of sessions. Conclusions: EE facilitates abstinence in males and females and after periods where incubation of craving may occur. This suggests that EE may benefit individuals attempting to abstain from heroin use and may aid in the development of long term treatment strategies.